A synthetic full backup is created by “stitching” together portions of a regular (or synthetic) full backup and one or more subsequent incremental backups. The metadata associated with such a backup can become highly fragmented, especially after multiple successive synthetics backups. For example, metadata of a synthetic backup may reference a portion of metadata of a prior backup, and a portion of the metadata of that prior backup may reference portions of metadata from even earlier backups, and so on, recursively, to some depth. The respective metadata for each referenced backup may reside in different locations on the storage media, requiring potentially many disparate containers or other logical storage units of data to be read (“loaded”) to access the metadata for a synthetic backup.
In de-duplicated storage systems, read efficiency may be improved by intentionally writing duplicates to ensure that data or metadata that may need to be accessed at the same time are stored together, even if some of the data (e.g., data “segments”) are known to be stored already, elsewhere on the system. However, typically there is a limit to how much duplicate data can be written. Also, de-duplication processing at the backup (or other de-duplicated) storage system may result in earlier-stored copies being deleted, potentially increasing the fragmentation of earlier backups.